Mesoporous aluminosilicates: preparation from Ca-A zeolite by treatment with ammonium fluorosilicate

Mao, R. Le Van; Vo, Nhat Tri; Sjiariel, Bernard; Lee, L.; Dénès, Georges

doi:10.1039/jm9920200595

Cited by 15 publications

(8 citation statements)

References 4 publications

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“…When zeolite Y was dealuminated by SiCl 4 , little mesoporosity was generated and most of the microporosity of the zeolite was preserved . Le Van Mao et al showed that the textural and adsorptive properties of Ca-A zeolite undergo significant changes upon mild leaching, controlled hydrothermal treatment, or chemical treatment with AFS . Aqueous AFS solution, under mild conditions (e.g., room temperature, pH ≈ 7.0), created slit-shaped mesopores with a distribution maximum at 14−20 nm; the average pore diameter depends on the rate of addition of the AFS solution to the leaching medium.…”

Section: 2 Hydrothermal and Chemical Treatmentsmentioning

confidence: 99%

Mesopore-Modified Zeolites: Preparation, Characterization, and Applications

et al. 2006

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Section: 2 Hydrothermal and Chemical Treatmentsmentioning

confidence: 99%

Mesopore-Modified Zeolites: Preparation, Characterization, and Applications

et al. 2006

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“…In order to retain the crystal structure of dealuminated zeolite crystal, the post dealumination can also be carried out in aqueous solutions containing ammonium hexafluorosilicate [20,21] and SiCl 4 [22][23][24]. This can heal the dealuminated framework sites with silicate species during the dealumination treatment.…”

Section: Post-synthetic Demetallation Of Zeolite Crystalsmentioning

confidence: 99%

“…In this route, the mesopores can be produced by base treatment that can leach out the Si species from the zeolite framework, which makes mesopores that are interconnected each other and accessible from the external surface of the zeolite crystal [26,27]. The desilication process is effective for high-silica zeolites (usually Si/Al [ 20) than high Al zeolites [28,29]. It was reported that mesoporous textures generated by the desilication process strongly depend on the concentration and distribution of Al within the zeolite crystals [26,28,30].…”

Section: Post-synthetic Demetallation Of Zeolite Crystalsmentioning

confidence: 99%

Hierarchically Nanoporous Zeolites and Their Heterogeneous Catalysis: Current Status and Future Perspectives

Somorjai

2014

Catal Lett

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The research field of hierarchically nanoporous zeolites has been growing at an enormous pace over the past decades. Hierarchically nanoporous zeolites have versatile structural properties such as high surface area and large pore volume that can alleviate diffusional limitations of conventional zeolites with solely microporous framework. In this review, various synthesis strategies to hierarchically nanoporous zeolites and their structural advantages in catalytic reactions will be reviewed. In the first part, many novel synthetic approaches for hierarchically nanoporous zeolites such as post-demetallation, softtemplating, hard-templating, and dual-pore-generating surfactant-directed methods will be introduced. In the second part, catalytic applications of hierarchically nanoporous zeolites on various chemical reactions involving isomerization, cracking, alkylation and oxidation will be discussed. The present comprehensive review will provide future opportunities and perspectives on the research of hierarchically nanoporous zeolites including their applications to catalytic reactions.

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“…[4][5][6][7]12]. The basic procedure was as follows: 2.7 g of NaX or 5.0 g of CaA zeolite (all in powder form) were placed into a Teflon beaker containing 200 cm 3 of 0.8 mol dm )3 ammonium acetate solution (pH of ca.…”

Section: Controlled Dealumination Of Nax and Caa Zeolitesmentioning

confidence: 99%

“…Unfortunately, these materials are known to be quite thermally and chemically unstable [3]. In the past, we have shown that mesoporous materials can be obtained from Al-rich zeolites by controlled dealumination using ammonium hexafluorosilicate (AHFS) as Al removing agent [4][5][6][7]. This is in contrast with more aggressive Al removing media such as mineral acids which usually lead to severe structural collapses and thus not very useful mesoporous materials because the latter are subject to numerous pore occlusions [8] or a lack of direct connection with the external surface of the treated zeolite particle [9].…”

Section: Introductionmentioning

confidence: 99%

Silica Nanoboxes as New Nano-structured Materials: Their Secondary Synthesis from Alumina-Rich Zeolites

Mao

Al-Yassir

et al. 2005

Catal Lett

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Novel silica nanoboxes were prepared by controlled dealumination of Na-X and Ca-A type zeolites using ammonium hexafluorosilicate (AHFS). The silica-richer the parent zeolite, the smaller the average pore size produced and the narrower the pore size distribution obtained. This was due to the specific reactivity of the extracting agent with the zeolite framework aluminum atoms. High temperature calcination of the dealuminated X-zeolite (ammonium form) resulted in mesoporous materials exhibiting an ink-bottle shape, a quite high surface area (330 m 2 /g, no micropores), an average pore diameter of 4.5 nm with a quite narrow pore size distribution (±1.0 nm) and finally, a pore opening diameter of 3.9 nm. The latter was determined by using the nitrogen sorption isotherms (BET technique) and related pore volume data. The sorption behavior also suggested the interconnecting character of the newly created nanoboxes. The periodicity of these nanoboxes throughout the mesoporous material was clearly shown by X-ray powder diffraction at very small angles. These materials, herein called monomodal nanoboxes because of the absence of micropores in the structure, were also thermally stable. Incorporation of orthosilicate into the obtained silica nanoboxes, in accordance with the recently developed technique for pore size engineering in zeolites, led to materials with smaller pore openings but having almost the same textural properties. Solid superacidic materials were prepared by incorporating a liquid superacid (triflic acid or trifluoromethanesulfonic acid) into the silica nanoboxes using the wet impregnation technique. The maximum triflic acid loading which did not significantly affect the mesoporous framework of the materials was 24 wt%. As a reference, the maximum loading of less acidic sulfuric acid was slightly lower. All this showed the high chemical stability of the silica nanoboxes for supporting very acidic species. Temperature-programmed desorption using a combined DTA/TGA system allowed the identification of the bound phases and some liquid phase of the loaded triflic acid.

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Mesoporous aluminosilicates: preparation from Ca-A zeolite by treatment with ammonium fluorosilicate

Cited by 15 publications

References 4 publications

Mesopore-Modified Zeolites: Preparation, Characterization, and Applications

Mesopore-Modified Zeolites: Preparation, Characterization, and Applications

Hierarchically Nanoporous Zeolites and Their Heterogeneous Catalysis: Current Status and Future Perspectives

Silica Nanoboxes as New Nano-structured Materials: Their Secondary Synthesis from Alumina-Rich Zeolites

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